From De-A-24 60 834 there is known a non-flammable organomineral foam which essentially comprises a reaction product of water-glass and a compound exhibiting at least two isocyanate groups, as well as a process for its preparation. In this process a water-glass solution is reacted with a compound exhibiting at least two isocyanate groups in the presence of one or more catalysts and one or more volatile substances as foaming agent(s). The catalysts used are amines and amino-alcohols known as inductors from polyurethane chemistry, 2,4,6-tris(dimethylaminomethyl)phenol being preferred. The volatile substances acting as "physical" foaming agents are liquids which evaporate while the water-glass is reacting with the isocyanate because of the heating effect produced. Examples thereof are monofluorotrichloromethane, dichlorodifluoromethane and trichlorotrifluoroethane.
In the process known from DE-A-24 60 834 there may be admixed as further additives polysiloxane-based silicone oils to adjust the cell structure, surface-active substances that simultaneously act as foam stabilisers, and flame-inhibiting additives.
The known process makes careful use of foaming agents to prepare foams of low apparent density (less than 100 kg/m.sup.3), haloalkanes such as trichlorofluoromethane being added, which are essentially responsible for the foaming of the reaction mixture. The carbon dioxide produced during the reaction of polyisocyanate and water-glass when a suitable NCO/Me.sub.2 O ratio (&gt;2) is set escapes uncontrolled in the known process and therefore is not available, or only to a negligible extent, for foam formation (Me in Me.sub.2 O stands for an alkali metal atom).
The use of haloalkanes as physical foaming agent required under the known process is undesirable from environmental aspects. Also, the organomineral foamed products obtained by the conventional process contain residual foaming agent in their closed cells which is released to the atmosphere with the lapse of time, this being undesirable, too. Hence, there is a need for a process to prepare organomineral foams (mixed organic/inorganic foamed materials) that can be carried out without the use of specially admixed foaming agents.
It is an object of the invention to provide novel organomineral foamed materials which do not contain residual foaming agents such as haloalkanes.
It is a further object of the invention to provide a novel process for the production of organomineral foamed materials which process is carried out without the use of physical foaming agents.
It is a further object of the invention to provide a novel process for the production of organomineral foamed materials which process is carried out without the use of physical foaming agents and which results in foamed organomineral products with defined and reproducible density, the products being free of residual foaming agents.